Even if my community size never grows beyond n=1 (which arguably it already has, since I've had several lengthy debates with people who aren't me), the level of error still can't be any worse than it would be had I not started the site (or posted my opinions anywhere) in the first place, right?

That said, yes, community is important. (I'm not sure "worried" is what you really meant, but I am certainly concerned about it.) Unfortunately, I don't see any options at present for improving the situation, given my time availability.

(This also strikes me as a further reason for "being bold" when making assertions -- or "setting the bar quite low" for verification, as dripgrind put it -- an extreme assertion is more likely to draw in a debate than a mild one. I don't go out of my way to make a given statement more extreme, but I try to avoid tempering what I say any more than is necessary to ensure defensibility based on the facts as I understand them.)